Is Taping Rigid Foam Above Grade a Waste of Time/Money?
Building a 2-story home in Florida with cement block exterior walls from the grade to the roof. For insulation, we’ll be filling the block’s holes with injected foam (R9) and applying 1″ rigid foam (R5) on the inside of the block walls. Furring strips are attached to the interior rigid foam to hang the drywall with an air gap in between the rigid foam and the drywall. My question is whether taping the interior rigid foam boards is a waste of time and money? Feels like it would be. Since the exterior walls are block with a painted stucco layer on top, air infiltration won’t be an issue. Both the water and vapor barriers are provided by the exterior paint/stucco layer. Florida is very humid, so there may be some vapor making its way into the wall cavity via the block, but that should be minimal as the exterior paint/stucco layer should retard that. It leads me to believe that spending contractor time taping the interior rigid foam will yield little to no benefit. Your thoughts?
I think your instincts here are correct. The primary reason for taping the seams would be to prevent air infiltration, but that’s not an issue here as the foam is inside of what will be a robust air barrier, and there’s little to no risk of condensation going the other way in your climate. Taping for vapor control isn’t that vital since, as has been widely discussed at FHB and GBA, a vapor retarder can be full of holes and still block most vapor.